Rework factory functions so they are placed now in a single file

Rework factory functions so they are placed now in a single file

	* backend/ev-document-factory.c:
	(ev_document_factory_get_from_mime),
	(ev_document_factory_get_all_mime_types), (get_document_from_uri),
	(ev_document_factory_get_document),
	(file_filter_add_mime_list_and_free),
	(ev_document_factory_add_filters):
	* backend/ev-document-factory.h:
	* properties/ev-properties-main.c: (ev_properties_get_pages):
	* shell/Makefile.am:
	* shell/ev-application.c:
	* shell/ev-job-xfer.c: (ev_job_xfer_run):
	* shell/ev-window.c: (ev_window_cmd_file_open),
	(ev_window_cmd_save_as):
	* thumbnailer/evince-thumbnailer.c: (evince_thumbnail_pngenc_get):

	Rework factory functions so they are placed now in a single
	file ev-document-factory.c